The present invention relates to a single-cylinder circular machine for knitting, hosiery or the like, with a device for actuating the cutter mounted on the dial.
Conventional single-cylinder circular machines for knitting or hosiery are composed of a needle cylinder which has a vertical axis and can be rotated about said axis and a dial which is arranged above and coaxially to the needle cylinder.
Hooks are usually arranged in the dial and can be actuated in a radial direction with respect to the dial axis in order to cooperate with the needles when forming particular kinds of knitting, such as for example the formation of a tubular border at one end of the item being formed.
The dial is usually equipped with a circular cutter which is arranged coaxially to the dial and has a plurality of teeth protruding radially. Said cutter is usually rigidly coupled to the dial, which is supported, so that it can rotate about its own axis, by an adapted frame arranged above the needle cylinder. On said frame, proximate to the cutter, there are one or more blades which rest on the upper face of the cutter proximate to the region of the teeth in order to cooperate with them in cutting the yarn.
Cutting the yarn becomes necessary at the end of a step in which the machine has knitted with a given yarn, or during the formation of patterns with yarns of different colors on the item. In this situation the yarns, at the end of the portion of the row of knitting to be formed with said yarns, are placed beyond the reach of the needles of the machine and are cut by means of the cutter and the blade. In practice, in order to cut the yarn, the yarn finger that dispenses it is moved into a position where it cannot be engaged by the needles of the machine and the yarn, which has remained hooked to the last needle of the machine that has taken it up, is stretched between said needle and the corresponding yarn finger and is engaged by the cutter, which rotates together with the needle cylinder and the dial. When the yarn thus engaged arrives at the cutter, it is cut.
Depending on the kind of weaving operation used to knit these yarns which are then cut, it is necessary to cut the yarn so as to leave a trailing portion which is sufficient to safely prevent said yarn from laddering. Accordingly, depending on the kind of weaving operation used to knit the yarns which are then cut, it is necessary to be able to vary the length of the trailing portion of yarn, i.e., of the part of yarn that usually remains on the reverse side of the item. A short length is undesirable because said yarn might ladder during the life of the item, while an excessive length is undesirable due to aesthetic reasons and for the convenience of the user and can cause yarns of nearby patterns to overlap.
With currently commercially available machines with the circular cutter coaxially fixed to the dial, the length of the trailing portion of the yarn can be changed only by varying the number of teeth of the cutter, in which the varying spacing between the varying number of teeth peripherally spaced about the axis of the cutter and dial determines the trailing yarn length. In practice, when a longer trailing portion of yarn is to be obtained, cutters having a reduced number of teeth and thus an increased tooth spacing are used, while when a shorter length is to be obtained, cutters having a greater number of teeth and thus a decreased tooth spacing are used.
Since in order to vary the length of the trailing portion of yarn it is necessary to replace the cutter, with currently commercially available machines it is practically impossible to change the length of the trailing portion of the yarns cut on a same item.